Humble Bundle Question

From personal experience humble bundle games have never expired, keys that may have expired may have been beta keys that were masked as actual giveaways or some press release keys that the developer decided to recall (although even this is very rare nowadays). As far as the games form humble bundle be it from the store, monthly or just from bundles they should never expire.
note - only games that expire are the ones that humble bundle gives away.

How long is too long before Humble Bundle games stop working?

They're not supposed to expire, however I read in some thread here that they only "guarantee" the availability of games of 60 days (seen in a thread where someone who bought a game and tried to get his key too late didn't manage to get it - he was refunded)

Gifts links are "bad", Keys are good, just dont wait 2 years before revealing a key.

Well, there's a chance that you are crazy, of course, but your post doesn't reflect that at all. From what I've got so far, gift links are a considerably more risky option.

So far (twice) HB support has been amazing. Both cases have been Gift links. The first one was entirely my fault and I even told HB that. I only asked if they could revoke it. They gave me a new one.

A few days ago I generated a gift link from the "Yogscast Jingle Jam 2016" So you can see its not new. There was a problem with the resulting key when the winner redeemed it. HB gave me a another key that I gave to the winner. It worked.

I always use HB Gift links if possible. If it comes down to it. I can tell HB who I gave the gift to and they can see if that is who used it. Anyone can use a key. A gift link is just like it sounds like. A gift your giving someone. As long as your not trading or selling it. This is its purpose.

Keys shouldn't expire unless stated otherwise and most of the times Humble is reliable. But there are two problems that sometimes occur:
1.) Gift links. This is the "right"/intended way for giveaways, but from time to time someone tells that a link didn't work anymore after some time, so it seems they aren't as trustworthy as keys. You should create them only right before sending them to the winner.
2.) Keys. In my opinion the simpler and safer way, but Humble doesn't like it. If one day you have a problem, contact support and they notice that you revealed keys for games which aren't in your own Steam library, they consider you to be a reseller and don't ever help you again.

Of course, the sooner you activate your games after buying them, the higher the chances that you can get a new key if anything isn't right. But you don't need to rush, many people wait weeks or months before giving a key away and 99% of all keys will still be working after years.

Don't generate a gift link/key until you're ready to use it. If you're giving it to someone else use a gift link rather than a key. If you do have any trouble with the gift link and have to contact support for a replacement DO NOT mention steamgifts or any other site - just say you gave the link to a friend.

You might have been reading something that was related to the recent Playstation bundle that HB had, which has only been the second or third one of those I believe. Those codes has an expiration date but only because of something on Sony's end. Normal Humble Bundle keys never expire.
As for the whole link or key thing, some people prefer receiving the link so that they can have it in their HB library and all of the info that comes with that as described above. If however you are a lazy jerk like me and you just want to use a key because it's faster and easier (especially when making a train or multiple GA's) then just use the key. The winner need not know where the game is coming from. That's your business and no one elses.

i've given away a lot of humble bundle games as gift links and never had a problem. they've been of varying ages from the beginning of humble gift links.

Let me put it that way , as someone who lost a fuck ton of money worth of games from Humble .

ff you buy a bundle and you already owned 1 of the games ... yet revealed the key.

There is solid chance that if in the future you have faulty key , they will just flat out refuse to help you , cause you are Key reseller or some shit .

I bough a bunch of stuff from there , with intent of giveaway , and a bunch of bundles i got with dupes.
Was saving them for my SG birthday ... but then it turned out , every single key was used .

Humble support said im key re seller and said they wont help me , and any future support i require will be ignored .

SO fuck humble .

When you press the generate gift link button, it assigns a key to that game, but it is hidden behind a link.
Generally, this means the winner has another hoop to jump through to activate the key, but it is a small disadvantage compared to the massive benefits:
With a gift link, you can easily check yourself if it is redeemed or not. If the link drops an error, it was used. If it is asking for email, it still works.
A gift link is Humble's official way to give a game to someone else and not for your personal account. If you have any issues later and you sent keys to other people (they can check the accounts that activated the keys through the developers), then they can refuse any support.

So, use gift links. Gift links are good, gift links were made with the intention of gifting them.